Portable laser diode scanning head

ABSTRACT

A portable laser diode scanning head, aimable at each symbol to be read, emits and receives non-readily-visible laser light, and is equipped with a trigger-actuated aiming light arrangement for visually locating and tracking each symbol. A compact laser diode optical train and an optical folded path assembly, as well as an interchangeable component design and an integral window construction for the head also are disclosed. An embodiment that employs a stationary folding mirror mounted in fixed stationary relationship with a curved collecting mirror and a lightweight, movable scanning mirror is disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of Ser. No. 07/784,619 Oct. 30, 1991now abandoned, which is a Continuation of Ser. No. 07/562,037 Aug. 2,1990 now abandoned which is a Continuation in part of Ser. No.07/454,144 Dec. 21, 1989 U.S. Pat. No. 5,021,641 which is a Division ofSer. No. 07/295,151 Jan. 9, 1989 U.S. Pat. No. 4,897,532 which is aDivision of Ser. No. 07/148,669 Jan. 26, 1988 U.S. Pat. No. 4,825,057which is a Division of Ser. No. 06/706,502 Feb. 28, 1985 abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to laser scanning systems forreading symbols such as bar code symbols. More particularly, the presentinvention relates to a lightweight, multi-component, portablelaser-diode scanning-head supportable by a user and aimable at eachsymbol to be read. Still more particularly, this invention relates to anaiming light arrangement for visually locating and, in some cases,tracking each symbol to be read when the head emits and/or receiveslight which is not readily visible and is, in effect, invisible to theuser; to a trigger which controls the aiming light arrangement; to alaser-diode optical assembly; to an optical element which reflects anaiming light beam but transmits non-readily-visible light; to ascanning/collecting/focusing mirror system; to an interchangeablecomponent design, wherein one or more components, as desired, arereceivable in a single handle of the head, or in interchangeable handleswhich are detachably mountable to the head; and to a light-blockingcover which overlies selected transparent portions of the head toprevent light from passing therethrough.

2. Description of the Prior Art

Various optical readers and optical scanning systems optically read barcode symbols applied to objects in order to identify the object byoptically reading the symbol thereon. The bar code symbol itself is acoded pattern comprised of a series of bars of various widths, andspaced apart from one another to bound spaces of various widths, thebars and spaces having different light-reflecting characteristics. Thereaders and scanning systems electro-optically decoded the coded patternto a multiple alpha-numerical digit representation descriptive of theobject. Scanning systems of this general type have been disclosed, forexample, in U.S. Pat. Nos. 4,251,798; 4,360,798; 4,369,361; 4,387,297;4,409,470 and 4,460,120, all of which have been assigned to the sameassignee as the instant application.

As disclosed in some of the above patents, a particularly advantageousembodiment of such a scanning system resided, inter alia, in emitting alaser light beam from a hand-held, portable laser scanning head whichwas supported by a user, aiming the head and, more particularly, thelaser light beam, at a symbol to be read, repetitively scanning thelaser beam in a series of scans across the symbol, detecting the scannedlaser light which is reflected off the symbol, and decoding the detectedreflected light. The laser light beam was usually, but not always,generated by a helium-neon gas laser which emitted red laser light at awavelength of about 6328 Angstrom units. This red laser light wasvisible to the user and, thus, the user, without difficulty, couldproperly aim the head and position and maintain the emitted red laserlight on and across the symbol during the scanning.

However, in the event that the laser light beam was generated by asemiconductor laser diode, as, by way of example, see U.S. Pat. Nos.4,387,297; 4,409,480 and 4,460,120, then the aiming of the head relativeto the symbol was rendered more difficult when the laser diode emittedlaser light which was not readily visible to the user. For some laserdiodes, the laser light was emitted at a wavelength of about 7800Angstrom units, which was very close to infrared light and was on theborderline of being visible. This laser diode light was visible to theuser in a darkened room, but not in a lit environment where ambientlight tended to mask out the laser diode light. Furthermore, if thelaser diode light was moving, for example, by being swept across thesymbol, and especially if the laser diode light was being swept at fastrates of speed on the order of a plurality of times per second, forexample, at a rate of 40 scans per second, then the laser diode lightwas not visible to the user, even in a darkened room. Hence, due to oneor more of such factors as the wavelength of the laser light, theintensity of the laser light, the intensity of the ambient light in theenvironment in which the laser light was operating, the scanning rate,as well as other factors, the laser diode light was rendered, in effect,"invisible", or, as alternately defined herein and in the claims, asbeing "non-readily visible".

This non-readily-visible laser diode light did not enable the user,however, to readily aim the laser diode light at the symbol, at leastnot without a great deal of difficulty and practiced effort because theuser could not see the laser diode light. The user was required to huntaround by trial and error, hope that the scanning laser diode light waseventually properly positioned on and across the symbol, and wait untilthe scanning system advised him, typically by the lighting of anindicator lamp or by the sounding of an auditory beeper, that the symbolhad indeed been successfully decoded and read. This hunting techniquewas a less-than-efficient and time-consuming procedure for readingsymbols, particularly in those applications where a multitude of symbolshad to be read every hour and every day.

Nevertheless, in the context of a laser scanning head which was desiredto be made as lightweight, miniature, efficient, inexpensive and easy touse as possible, the laser diode was more advantageous than thehelium-neon gas laser, despite the non-readily-visible laser diode lightcharacteristic, because the laser diodes were smaller, were lighter inweight, had reduced power requirements (voltage supplies on the order of12 v DC or less), were directly modulated for synchronous detection andfor increased signal-to-noise ratios, etc., as compared to such gaslasers.

However, despite the above advantages, certain optical properties of thelaser diode beam itself, aside from its invisibility, did not readilyenable the laser diode beam to be focused to a desired spot size (e.g. a6 to 12 mils circular spot) at a given reference plane exteriorly of thehead, and to maintain the spot size within specified tolerances ateither side of the reference plane within a predetermined depth of focusor field, i.e. the working distance in which a symbol located anywherewithin the field can be successfully decoded and read. For example, thelonger wavelength of the laser diode beam, as compared to that of thehelium-neon gas laser, dictated a shorter working distance for the samespot size. The laser diode beam was also highly divergent, divergeddifferently in different planes, and was non-radially symmetrical. Thus,whereas the gas laser beam had the same small divergence angle of aboutone milliradian in all planes perpendicular to the longitudinaldirection of beam propagation, the laser diode beam had a largedivergence angle of about 200 milliradians in the plane parallel to thep-n junction plane of the diode, and a different larger divergence angleof about 600 milliradians in the plane perpendicular to the p-njunction. In the single transverse mode (TEM_(oo)), the gas laser beamhad a radially symmetrical, generally circular cross-section, whereasthe laser diode beam had a non-radially-symmetrical, generally ovalcross-section.

By way of example, in a so-called geometrical approach to solving theaforementioned focusing problem, and ignoring the non-radiallysymmetrical nature of the laser diode beam, optical magnificationfactors in excess of 80 were obtained if one wished to focus the beamspot to have about a 9.5 mil spot diameter at a reference plane locatedabout 31/2" from the head. However, such high magnification factorsdictated that, if one optical focusing element were employed (e.g. seeU.S. Pat. No. 4,409,470), it would have to be critically manufactured,positioned and adjusted. If one employed several optical focusingelements in a lens system designed with a large numerical aperture, i.e.on the order of 0.25, as suggested by U.S. Pat. No. 4,387,297 to accepta large divergent laser diode beam and to distribute the magnificationamong the elements, then the mechanical tolerances for each elementwould be looser, and the positioning and adjustment procedures would beeasier. However, a multiple, as opposed to a single, optical elementdesign occupied more space within, and increased the weight and expense,of the head.

Also, although an oval laser diode beam spot was, in certain cases,desirable in ignoring voids in, and dust on, the symbol, as well as inrendering the light-dark transitions more abrupt, as compared to acircular gas laser beam spot during a scan across a symbol, theseadvantageous features occurred when the longer dimension of the ovalspot was aligned along the height of the symbol, Thus, to obtain suchdesirable features, the laser diode beam had to be correctly aligned ina certain orientation relative to the symbol. When the symbols wereoriented in a random manner relative to the laser diode beam, the headhad to be frequently manipulated to correctly orient the laser diodebeam on the symbol. This further aggravated thealready-less-than-efficient and time-consuming procedure for readingsymbols, particularly on a mass basis, with laser diode light. Althoughit was possible to circularize the oval laser diode beam spot using ananamorphic collimator, this further increased the number of opticalelements, the space, the weight and the expense.

Still another drawback inherent in earlier laser scanning heads, both ofthe gas laser and laser diode type, was that they were not readilyadaptable to different applications. Different end users had differentrequirements. Whereas one user might want the electronic circuitry fordecoding the detected reflected light to data descriptive of the symbol,and for controlling the decoding, to be mounted in the head, anotheruser would require this electronic circuitry to be located remotely fromthe head. Still other users had different requirements concerningwhether or not to locate a rechargeable power source or a data storageeither locally in, or remote from, the head. Thus, the prior laserscanning systems had, more or less, to be custom-made for each user, andthis was not altogether desirable in terms of manufacturing ormarketing. Also, if the user wished to change the system requirements,the user had to forego the change, or obtain another system.

Yet another disadvantage associated with earlier laser scanning headswas that each had a discrete light-transmissive window mounted thereon.The discrete window was a separate piece which had to be glued in placeand, hence, over time, the window sometimes came free of its gluedmounting, particularly if the head was frequently subjected tomechanical shock and abuse. Once the window became disengaged, moisture,dust and other such contaminants were free to enter the interior of thehead, thereby coating the optics and the electronic circuitry therein,and possibly interfering with their intended operation.

SUMMARY OF THE INVENTION

1. Objects of the Invention

It is a general object of this invention to overcome the above-describeddrawbacks of the prior art laser scanning systems.

It is another object of this invention to enable a user to readily aim ahead and, more particularly, to direct at a symbol a non-readily-visiblelaser light beam emitted from the head at, and/or to collectnon-readily-visible reflected laser light reflected from, the symbol.

It is a further object of this invention to enable a user to readily aima non-readily-visible laser beam emitted by a semiconductor laser diodeon and across a symbol prior to and during a scan of the symbol.

Yet another object of this invention is to eliminate the trial-and-errorhunting techniques, particularly at long working distances, in aiming asemiconductor laser diode beam at a symbol.

Still another object of this invention is to increase the efficiency andreduce the time involved in optically reading a symbol with asemiconductor laser diode beam.

A still further object of this invention is to accurately locate asymbol with a semiconductor laser diode-based scanner prior to a scan,and to accurately track the symbol with the semiconductorlaser-diode-based scanner during the scan.

Another object of the invention is to readily enable a highly divergent,non-radially symmetrical, long wave-length, semiconductor laser diodebeam having a generally oval beam cross-section to be focused to adesired beam spot size at a given reference plane exteriorly of thehead, and maintained at the spot size within specified tolerances ateither side of the reference plane within a predetermined depth of fieldwithout requiring a single high-precision, high-magnification opticalfocusing element to be manufactured or precisely positioned relative tothe diode, and without requiring multiple optical focusing elements tooccupy increased space within the head.

Another object of the invention is to provide an efficient and compactoptical folded path assembly within the head having a novel opticalelement for transmitting a semiconductor laser diode beam, including astationary folding mirror mounted on or affixed to a stationary, concavecollecting mirror, and a lightweight, substantially flat scanningmirror.

A further object of the invention is to provide a multi-position,manually-depressible trigger for controlling the operation of an aiminglight arrangement, as well as that of the laser scanning system.

Still another object of the invention is to provide a modular design forthe components in the head, wherein different components are receivablein either a single handle, or in readily interchangeable handles,mounted on the head, for readily adapting the head to differentrequirements of different users.

Yet another object of the invention is to provide a very lightweight,streamlined, compact, hand-held, fully portable, easy-to-manipulate,non-fatiguing laser diode scanning head and/or system supportableentirely by a user during the optical reading of symbols, especiallyblack and white symbols used in industrial applications, but also barcode symbols of the type known as the Universal Product Code (UPC).

An additional object of the invention is to seal the interior of a headfrom contaminants.

2. Features of the Invention

In keeping with these objects and others which will be apparent to thoseof skill in the art, one feature of the invention resides in an aiminglight arrangement for use in aiming a hand-held laser scanning head in alaser scanning system for reading symbols at which the head is aimed.Several components are conventionally mounted in the head. For example,means, e.g. a semiconductor laser diode or possibly a gas laser, areprovided within the head for generating an incident laser beam. Opticmeans, e.g. a positive lens, a negative lens, reflecting mirrors, orother optical elements, are also provided within the head for opticallymodifying, i.e. forming, and directing the incident laser beam along afirst optical path toward a reference plane located exteriorly of thehead and lying in a plane generally perpendicular to the direction ofpropagation of the incident laser beam, and to a symbol located in aworking distance range in the vicinity of the reference plane. Forconvenience, a symbol that is located between the reference plane andthe head is defined hereinafter as a "close-in" symbol, whereas a symbolthat is located on the other side of the reference plane away from thehead is defined as a "far-out" symbol.

Laser light is reflected off the symbol, and at least a returningportion of the reflected laser light travels along a second optical pathaway from the symbol back toward the head. Scanning means, e.g. ascanning motor having a reciprocally-oscillatable output shaft on whicha reflecting surface such as a scanning mirror is mounted, are mountedin the head for scanning the symbol in a scan, and preferably at aplurality of sweeps per second, across the symbol in a repetitivemanner. The returning portion of the reflected laser light has avariable light intensity across the symbol during the scan which is due,in the case of a bar code symbol, to the different light-reflectivecharacteristics of the bars and spaces which constitute the symbol.

The head also comprises sensor means, e.g. one or more photodiodes, fordetecting the variable light intensity of the returning portion of thereflected laser light over a field of view, and for generating anelectrical analog signal indicative of the detected variable lightintensity. Signal processing means are also mounted in the head forprocessing the analog electrical signal, and usually for processing theanalog signal to a digitized electrical signal, which can be decoded todata descriptive of the symbol being scanned. The scanning means isoperative for scanning either the incident laser beam itself across thesymbol, or the field of view of the sensor means, or both.

Sometimes, but not always, decode/control electronic circuitry isprovided locally in, or remotely from, the head. The decode/controlelectronic circuitry is operative for decoding the digitized signal tothe aforementioned data, for determining a successful decoding of thesymbol, and for terminating the reading of the symbol upon thedetermination of the successful decoding thereof. The reading isinitiated by actuation of a manually-actuatable trigger means providedon the head, and operatively connected to, and operative for actuating,the laser beam generating means, scanning means, sensor means, signalprocessing means, and decode/control means. The trigger means isactuated once for each symbol, each symbol in its respective turn. In apreferred embodiment, the actuation of the trigger means causes theactuation of the decode/control means which, in turn, causes theactuation of the laser beam generating means, scanning means, sensormeans and signal processing means.

In conventional usage, the head, which is supported by a user in his orher hand, is aimed at each symbol to be read, and once the symbol islocated, the user actuates the trigger means to initiate the reading.The decode/control means automatically alerts the user when the symbolhas been read so that the user can turn his or her attention to the nextsymbol, and repeat the reading procedure.

As noted above, a problem arises when the incident laser beam or thereflected laser light is not readily visible, which can occur due to oneor more of such factors as the wavelength of the laser light, the laserlight intensity, the ambient light intensity, the scanning rate, as wellas other factors. Due to such "invisibility" the user cannot see thelaser beam and does not know readily when the invisible laser beam ispositioned on the symbol, or whether the scanning laser beam is scanningover the entire length of the symbol.

Hence, in accordance with this invention, the aiming light arrangementassists the user visually to locate, and aim the head at, each symbolwhen such non-readily-visible laser light is employed. The aiming lightarrangement includes means including an actuatable aiming light source,e.g. a visible light emitting diode, mounted in the head, andoperatively connected to the trigger means, and operative, when actuatedby the trigger means, for generating an aiming light beam whose light isreadily visible to the user; and aiming means, also mounted in the head,for directing the aiming light beam along an aiming light path from theaiming light source toward the reference plane and to each symbol inturn, visibly illuminating at least a part of the respective symbol andthereby locating the latter for the user. The aiming light path lieswithin, and preferably extends parallel to, either the first opticalpath or the second optional path, or both, in the portion of such pathswhich lie exteriorly of the head. Thus, the user is assisted incorrectly aiming the head at the respective symbol to be read.

In one advantageous embodiment, the aiming light arrangement directs asingle aiming light beam to each symbol to illuminate thereon agenerally circular spot region within the field of view, and preferablynear the center of the symbol. It is further advantageous if this singlespot region remains stationary or static during the scanning of thesymbol so that both close-in and far-out symbols can be seen and locatedby the user, both prior to and during the scan. However, one drawbackassociated with such static single beam aiming is that the user cannottrack the linear scan of the scanning beam across the symbol during thescan. In other words, the user does not know where the ends of the laserscans are and, hence, does not know whether the linear scan is extendingacross the entire length of the symbol, or is tilted relative thereto.

In another advantageous embodiment, the aiming light arrangement directsa pair of aiming light beams to each symbol to illuminate thereon a pairof generally circular spot regions that are within, and spaced apart ofeach other along, the field of view. Preferably, the two spot regionsare located at, or near, the ends of the linear scan, as well asremaining stationary or static during the scanning of the symbol so thatboth close-in and far-out symbols not only can be seen and located bythe user both prior to and during the scan, but also can be trackedduring the scan. However, one drawback associated with such static twinbeam aiming is that two aiming light sources and associated optics arerequired, and this represents increased system complexity, weight, sizeand expense.

In still another advantageous embodiment, the aiming light arrangementdirects a single aiming light beam to a reciprocally oscillatingfocusing mirror operative to sweep the aiming light across each symbolto illuminate thereon a line region extending along the field of view.Such dynamic single beam aiming is advantageous because close-in symbolscan be more readily seen, located and tracked, as compared to staticaiming. However, one drawback associated with such dynamic aiming isthat far-out symbols cannot readily be seen, located or tracked,particularly when the focusing mirror is being swept at high scan rateson the order of 40 scans per second, due to the inherently reducedintensity of the light collected by the human eye.

In a further advantageous embodiment, the aiming light arrangementdirects a single aiming light beam to a focusing mirror which has astationary state and a reciprocally oscillating state. Initially, theaiming light beam is reflected off the stationary focusing mirror toeach symbol to illuminate thereon a spot region within the field ofview, preferably near the center of the symbol, prior to the scan of thesymbol to locate the same. Thereupon, the focusing mirror is caused toreciprocally oscillate to reflect the aiming light beam to the symbol tosweep the aiming light beam across the symbol to illuminate thereon aline region extending along the field of view, thereby tracking thesymbol. This combination static/dynamic aiming is very desirable becauseit enables a user to track a close-in symbol during the scan (which wasnot readily possible with only static single beam aiming), and alsoenables the user to at least locate a far-out symbol prior to the scan(which was not readily possible with only dynamic aiming). Since, in themajority of cases, the symbols to be read will be close-in symbols, theinability to track the far-out symbol in the combination static-dynamicaiming embodiment is not critical.

To implement such combination static/dynamic aiming, it is advantageousif the trigger means has multiple positions and is operativelyconnected, either directly or indirectly via the decode/control means,to the aiming light source, as well as the oscillatable focusing mirror.In a first position, or off state, for the trigger, all of thecomponents in the head are deactivated. In a second position, or firstoperational state, the aiming light source is activated, and thefocusing mirror is positioned in a predetermined stationary position,e.g. in a center position, for a predetermined time, so that the aimingbeam can illuminate a center spot region of the symbol to be read. In athird position, or second operational state, all of the other componentsin the head, including those responsible for reciprocally oscillatingthe focusing mirror, are activated, thereby initiating the reading ofthe symbol and the illumination of a line region along the field ofview.

All of the above aiming light arrangement embodiments are in directcontrast to those that were provided on wand or pen readers which weremanually positioned on, or at a small distance from, a symbol, andthereupon which were manually dragged or moved across the symbol.Skilled users were generally required to effect the aforementionedmovement because criticality in the manipulation of the angle of the penrelative to the symbol, the pen speed, the uniformity of the pen speed,and other factors were necessary. In any event, the manual reader onlyresults, at best, in one scan per manual movement and, if the symbol wasnot successfully read on the first attempt, then the user had to repeatthe manual scan again and again.

Another feature of this invention resides in the novel optic means forfocusing the highly divergent, non-radially-symmetrical laser diode beamhaving a generally oval beam cross-section. Advantageously, the opticmeans comprises a focusing lens, e.g. a plano-convex lens, and anaperture stop located in the first optical path adjacent the focusinglens. The aperture stop may have a circular, rectangular or ovalcross-section which is smaller than the beam cross-section at theaperture stop so as to permit a portion of the incident laser diode beamto pass through the aperture stop en route to the symbol. The wallsbounding the aperture stop obstruct and prevent the remaining portion ofthe incident laser diode beam from passing through the aperture stop enroute to the symbol. Such beam aperturing is in direct contrast to priorart designs, such as disclosed in U.S. Pat. No. 4,409,470, wherein theincident laser diode beam is deliberately permitted to travelunobstructedly through an aperture en route to the symbol. Such beamaperturing reduces the numerical aperture from large values on the orderof 0.15 to 0.45 to a value below 0.05 and significantly decreases theoptical magnification factor so that a single focusing lens can be usedto achieve the aforementioned advantages associated therewith. Althoughsuch beam aperturing is at the expense of output power of the laserdiode, the advantages achieved are well worth such expense, andsufficient output power remains in the portion of the incident laserdiode beam that passes through the aperture stop to read the symbol.

Although the use of aperture stops is well known in optical systems,such beam aperturing is believed to be novel and unobvious in laserscanning systems for reading symbols. As previously mentioned, anaperture stop decreases the power in the portion of the incident laserdiode beam that impinges the symbol and, as a general rule, a laserscanning system designer does not deliberately want to throw away power,particularly in that portion of the incident beam that impinges andscans the symbol, since less power is contained in the laser lightreflected off and collected from the symbol.

In addition, it is well known that for a given beam cross-section, i.e.spot size, of the incident laser beam, the depth of focus in an opticalsystem having an aperture stop will be less than that for an opticalsystem which does not have an aperture stop. Since, as a general rule, alaser scanning system designer wants as large a depth of focus aspossible--so that the working distance is correspondingly as large aspossible the use of an aperture stop is something to be avoided.

It is also well known that the smallest laser beam spot size that can betheoretically obtained in an optical system having an aperture stop willbe larger than that for an optical system which does not have anaperture stop. Hence, for those applications where a very small beamspot size is desired, one would not turn to using an aperture stop.

In an optical laser system which does not have an aperture stop, thelaser beam spot cross-section has a gaussian brightness distributioncharacteristic. By contrast, when an aperture stop is employed, lightdiffraction causes light rings or fringes in the beam spot. Such lightrings or fringes effectively cause the beam spot size to increase, aswell as other undesirable effects. The undesirably increased beam spotsize is still another reason why an aperture stop is not used in laserscanning systems.

On this latter point, the use of an aperture stop dictates that complexmathematics in accordance with general diffraction theory be employed todesign the optical system. Since it is more often the case that laserscanning system designers work with gaussian beam mathematics, which issimpler than diffraction mathematics, this represents still anotherpossible reason why the use of an aperture stop in a laser scanningsystem has not heretofore been proposed.

A particularly compact optical folded path assembly is achieved when anoptical element such as a so-called "cold mirror" is utilized to reflectthe visible aiming light beam to a collecting mirror of the sensormeans, but to transmit therethrough the reflected laser diode lightreflected by the symbol and collected by the collecting mirror. Stillanother efficient aspect of the overall optical assembly is to integratethe collecting mirror for the reflected laser light, together with theaforementioned scanning mirror for the incident laser diode beam, aswell as with the aforementioned focusing mirror for the aiming lightbeam into a multi-purpose mirror of one-piece construction.

Alternatively, the optical assembly may include a stationary,combination folding/collecting mirror assembly and a simple,light-weight reciprocally oscillatable scanning mirror. Such an opticalassembly provides flexibility in the placement of various componentswithin the scanning head and, because the scanning mirror islight-weight, provides improved control over the scanning pattern of thelaser-light beam. The use of the light-weight scanning mirror alsoreduces wear on the scanning motor attached to the scanning mirrorextending the life of the motor.

Another highly desirable feature is embodied in an interchangeablecomponent design for the head so that a manufacturer can readily adaptthe head to suit the particular requirements of each user. Thus,different components may be contained in a single handle for the head,or in a plurality of interchangeable handles for the head, therebyreadily adapting the head to suit the user and eliminating the laboriouscustom-made heads of the prior art.

Still another advantageous feature resides in eliminating the mountingof a discrete window on the head, and preventing the possibility thatsuch a window could become disengaged from its mounting and expose theinterior of the head to moisture, dust and other contaminants whichcould, under certain conditions, affect the operation of the head. Tothis end, at least a portion of the head is made of a one-piecetransparent material construction, and a cover of light-blockingmaterial is arranged over the transparent portions of the head to blocklight from passing therethrough, but leaving other transparent portionsof the head uncovered so that the other transparent portions may serveas the aforementioned window. It is further desirable to constitute thecover of a thick cushionable, yieldable material such as rubber toprovide a measure of shock resistance for the head.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe understood from the following description of specific embodimentswhen read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a portable laser diode scanning head inaccordance with this invention;

FIG. 2 is an enlarged cross-sectional view taken on line 2--2 of FIG. 1;

FIG. 3 is a section view taken on line 3--3 of FIG. 2;

FIG. 4 is an enlarged sectional view taken on line 4--4 of FIG. 2;

FIG. 5 is an enlarged detail view showing the trigger assembly in afirst operational state;

FIG. 6 is a view analogous to FIG. 5, but in a second operational state;

FIG. 7 is a view of a detachable battery pack accessory to the head ofFIG. 1;

FIG. 8 is an enlarged sectional view of a one-piecescanning/collecting/focusing mirror component as taken along line 8--8of FIG. 1;

FIG. 9 is an enlarged view of a symbol and the parts thereof which areimpinged upon, and reflected from, by laser light;

FIG. 10 is a schematic view of a static single beam aiming arrangement;

FIG. 11 is an enlarged view of a symbol and the parts thereof which areilluminated by static single beam, or by twin beam aiming;

FIG. 12 is a schematic view of a static twin beam aiming arrangement;

FIG. 13 is an enlarged view of a symbol and the parts thereof which areilluminated by a dynamic single beam aiming;

FIG. 14 is a view analogous to FIG. 2, but of a currently preferredcommercial embodiment of the head in accordance with this invention;

FIG. 15 is a schematic view of an alternative optical assembly that isuseful in the present invention; and

FIG. 16 is a schematic view of a laser scanning head showing placementof the optical assembly of FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-8 of the drawings, reference numeral 10generally identifies a lightweight (less than one pound), narrow-bodied,streamlined, narrow-snouted, hand-held, fully portable,easy-to-manipulate, non-arm-and-wrist fatiguing laser scanning headsupportable entirely by a user for use in a laser scanning systemoperative for reading, scanning and/or analyzing symbols. A user can aimthis scanning head prior to, and during the reading of symbols, eachsymbol in its turn. The term "symbol" as used herein, is intended tocover indicia composed of different portions having differentlight-reflective properties at the wavelength of the light source, e.g.a laser, being utilized. The indicia may be the aforementioned black andwhite industrial symbols, e.g. Code 39, Codabar, Interleaved 2 of 5,etc., and also the omnipresent UPC bar code symbol. The indicia may alsobe any alphabetic and/or numeric characters. The term "symbol" is alsointended to cover indicia located in a background field, wherein theindicia, or at least a portion thereof, have a differentlight-reflective property than that for the background field. In thislatter definition, the "reading" of the symbol is of particular benefitin the fields of robotics and object recognition.

As shown in FIGS. 1-3, the head 10 includes a generally gun-shapedhousing having a handle portion 12 of generally rectangularcross-section, generally vertically elongated along a handle axis, and agenerally horizontally elongated, narrow-bodied barrel or body portion14. The cross-sectional dimension and overall size of the handle portion12 is such that the head 10 conveniently can fit and be held in a user'shand. The body and handle portions are constituted of a lightweight,resilient, shock-resistant, self-supporting material, such as asynthetic plastic material. The plastic housing preferably isinjection-molded, but can be vacuum-formed or blow-molded to form athin, hollow shell which bounds an interior space whose volume measuresless than about 50 cubic inches and, in some applications, about 25cubic inches or less. Such specific values are not intended to beself-limiting, but to provide a general approximation of the overallmaximum size and volume of the head 10.

As considered in an intended position of use as shown in FIGS. 1-3, thebody portion 14 has a front prow region having an upper front wall 16and a lower front wall 18 which forwardly converge toward each other andmeet at a nose portion 20 which lies at the foremost part of the head.The body portion 14 also has a rear region having a rear wall 22 spacedrearwardly of the front walls 16, 18. The body portion 14 also has a topwall 24, a bottom wall 26 below the top wall 24, and a pair of opposedside walls 28, 30 that lie in mutual parallelism between the top andbottom walls.

A manually-actuatable, and preferably depressible, trigger 32 is mountedfor pivoting movement about a pivot axis 34 on the head in aforwardly-facing region where the handle and body portions meet andwhere the user's forefinger normally lies when the user grips the handleportion in the intended position of use. The bottom wall 26 has atubular neck portion 36 which extends downwardly along the handle axis,and terminates in a radially-inwardly extending collar portion 38 ofgenerally rectangular cross-section. The neck and collar portions have aforwardly-facing slot through which the trigger 32 projects and ismoved.

The handle portion 12 has a radially-outwardly extending upper flangeportion 40 of generally rectangular cross-section which also has aforwardly-facing slot through which the trigger 32 projects and ismoved. The upper flange portion 40 is resilient and deflectable in aradially-inward direction. When the upper flange portion 40 is insertedinto the neck portion 36, the upper flange portion 40 bears against thecollar portion 38 and is radially-inwardly deflected until the flangeportion 40 clears the collar portion 38, at which time, the upper flangeportion 40, due to its inherent resilience, snaps back to its initialundeflected position and engages behind the collar portion with asnap-type locking action. To disengage the handle portion from the bodyportion, the upper part of the handle portion is sufficiently deflecteduntil the upper flange portion 40 again clears the collar portion, andthereupon the handle portion can be withdrawn from the neck portion 36.In this manner, handle portion 12 can be detachably snap-mounted andde-mounted from the body portion 14 and, as explained below, anotherhandle portion from a set of interchangeable handle portions, eachcontaining different components of the laser scanning system, may bemounted to the body portion to adapt the head 10 to different userrequirements.

A plurality of components are mounted in the head and, as explainedbelow, at least some of them are actuated by the trigger 32, eitherdirectly or indirectly, by means of a control microprocessor. One of thehead components is an actuatable laser light source (see FIG. 4), e.g. asemiconductor laser diode 42, operative, when actuated by the trigger32, for propagating and generating an incident laser beam whose light,as explained above, is "invisible" or non-readily visible to the user,is highly divergent, is non-radially symmetrical, is generally oval incross-section, and has a wavelength above 7000, e.g. about 7800,Angstrom units. Advantageously, the diode 42 is commercially availablefrom many sources, e.g. from the Sharp Corporation as its Model No.LT020MC. The diode may be of the continuous wave or pulse type. Thediode 42 requires a low voltage (e.g. 12 v DC or less) supplied by abattery (DC) source which may be provided within the head, or by arechargeable battery pack accessory 44 (see FIG. 7) detachably mountedon the head, or by a power conductor in a cable 46 (see FIG. 2)connected to the head from an external power supply (e.g. DC source).

As best shown in FIG. 4, the laser diode 42 is mounted on a printedcircuit board 48. An optical assembly is mounted in the head andadjustably positioned relative to the diode 42 for optically modifyingand directing the incident laser beam along a first optical path towarda reference plane which is located exteriorly of the head, forwardly ofthe nose portion 20, and which lies generally perpendicular to thelongitudinal direction along which the incident laser beam propagates. Asymbol to be read is located in the vicinity of the reference plane,either at, or at one side, or at an opposite side, of the referenceplane, that is, anywhere within the depth of focus or field of theoptically modified incident laser beam, the depth of focus or field alsobeing known as the working distance in which the symbol can be read. Theincident laser beam reflects off the symbol in many directions, and thatportion of the reflected laser light which travels along a secondoptical path away from the symbol back toward the head is known hereinas the returning portion which, of course, also is non-readily visibleto the user.

As best shown in FIG. 4, the optical assembly includes an elongated,cylindrical optical tube 50 having at one end region a cylindrical bore52 in which an annular casing portion of the diode 42 is snugly receivedto hold the diode in a fixed position, and at the opposite end region ofthe optical tube 50 a lens barrel 54 is mounted for longitudinalmovement. The lens barrel 54 includes an aperture stop 56, blocking wallportions 58 surrounding and bounding the aperture stop 56, andcylindrical side wall portions 60 which bound an interior space.

The optical assembly further includes a focusing lens 62, e.g. aplano-convex lens, located within the interior space of the side wallportions 60 in the first optical path, and operative for focusing theincident laser beam at the reference plane. The aperture stop 56 may belocated on either side of the lens 62, but preferably on the downstreamside. A biasing means or tensioned coil spring 64 is located within theoptical tube, and has one coil end bearing against a casing portion ofthe diode, and another coil end bearing against a planar side of thelens 62. The spring 64 constantly urges the lens 62 against the blockingwall portions 58, thereby fixedly locating the lens 62 relative to theaperture stop 56. The lens 62 and aperture stop 56 are jointly movedwhen the lens barrel 54 is longitudinally moved. The side wall portions60 are initially received in a threaded or sliding relationship with aninner circumferential wall bounding the optical tube 50, and arethereupon fixed, e.g. by gluing or clamping, to the innercircumferential wall when a desired longitudinal spacing between thelens 62 and the aperture stop 56, on the one hand, and the diode 42, onthe other hand, has been obtained. The longitudinal movement between theside wall portions 60 and the inner circumferential wall of the tube 50constitutes an adjustable positioning means for the lens 62 and theaperture stop 56, and the fixing in position of the lens and theaperture stop relative to the diode constitutes a means for fixedlylocating the lens and the aperture stop at a predetermined spacing fromthe diode.

The aperture stop 56 has a cross-section which is smaller than thecross-section of the incident laser beam at the aperture stop 56,thereby permitting only a portion of the incident laser beam to passthrough the aperture stop 56 downstream along the first optical path enroute to the symbol. The blocking wall portions 58 obstruct theremaining portion of the incident laser beam, and prevent the remainingportion from passing through the aperture stop 56. The aperture stopcross-section preferably is circular for ease of manufacture, but alsomay be rectangular or oval, in which case, the longer dimension of therectangular or oval cross-section is aligned with the larger divergenceangle of the incident laser beam to transmit more energy to the symbol.

In accordance with diffraction optics law, the size of the requiredincident beam cross-section at the reference plane is determined, interalia, by the size of the aperture stop, the wavelength of the incidentbeam, and the longitudinal distance between the lens 62 and thereference plane. Thus, assuming the wavelength and longitudinal distanceremain the same, the beam cross-section at the reference plane can beeasily controlled by controlling the size of the aperture stopcross-section. The placement of the aperture stop downstream, ratherthan upstream, of the lens 62 avoids also taking the tolerances of thelens into consideration upon determination of the beam cross-section atthe reference plane.

The aperture stop 56 is positioned in the center of the laser diode beamso that the intensity of light is approximately uniform in the planesboth perpendicular and parallel to the p-n junction, i.e. the emitter,of the diode 42. It will be noted that, due to the non-radial symmetryof the laser diode beam, the light intensity in the plane perpendicularto the p-n junction is brightest in the center of the beam and thenfalls off in the radially outward direction. The same is true in theplane parallel to the p-n junction, but the intensity falls off at adifferent rate. Hence, by positioning a preferably circular, smallaperture in the center of a laser diode beam having an oval, largercross-section, the oval beam cross-section at the aperture will bemodified to one that is generally circular, and the light intensity inboth of the planes perpendicular and parallel to the p-n junctionapproximately is constant. The aperture stop preferably reduces thenumerical aperture of the optical assembly to below 0.05, and permitsthe single lens 62 to focus the laser beam at the reference plane.

In a preferred embodiment, the approximate distance between the emitterof the laser diode 42 and the aperture stop 56 ranges from about 9.7 mmto about 9.9 mm. The focal distance of the lens 62 ranges from about 9.5mm to about 9.7 mm. If the aperture stop 56 is circular, then itsdiameter is about 1.2 mm. If the aperture stop 56 is rectangular, thenits dimensions are about 1 mm by about 2 mm. The beam cross-section isabout 3.0 mm by about 9.3 mm just before the beam passes through theaperture stop 56. These merely example distances and sizes enable theoptical assembly to modify the laser diode beam and focus it to have abeam cross-section of about 6 mils to about 12 mils at a reference planeabout 3 inches to about 4 inches from the nose portion 20. The workingdistance is such that a close-in symbol, as previously defined, can belocated anywhere from about 1 inch away from the nose portion 20 to thereference plane, and a far-out symbol, as previously defined, can belocated anywhere from the reference plane to about 20 inches away fromthe reference plane.

The portion of the incident laser beam that passed through the aperturestop 56 is directed rearwardly by the optical assembly along an opticalaxis 102 within the head to a generally planar scanning mirror 66 forreflection therefrom. The scanning mirror 66 forwardly reflects thelaser beam impinging thereon along another optical axis 104 through aforwardly-facing, laser-light-transmissive window 68 mounted on theupper front wall 68, and to the symbol. As best shown in FIG. 9, arepresentative symbol 100 in the vicinity of the reference plane isshown and, in the case of a bar code symbol, is comprised of a series ofvertical bars spaced apart of one another along a longitudinaldirection. The reference numeral 106 denotes the generally circular,invisible, laser spot subtended by the symbol. The laser spot 106 inFIG. 9 is shown in an instantaneous position, since the scanning mirror66, when actuated by the trigger 32, is, as explained below,reciprocally and repetitively oscillated transversely to sweep theincident laser beam lengthwise across all the bars of the symbol in alinear scan. The laser spots 106a and 106b in FIG. 9 denote theinstantaneous end positions of the linear scan. The linear scan can belocated anywhere along the height of the bars provided that all the barsare swept. The length of the linear scan is longer than the length ofthe longest symbol expected to be read and, in a preferred case, thelinear scan is on the order of 5 inches at the reference plane.

The scanning mirror 66 is mounted on a scanning means, preferably ahigh-speed scanner motor 70 of the type shown and described in U.S. Pat.No. 4,387,397, the entire contents of this patent being incorporatedherein by reference and made part of the instant application. For thepurposes of this application, it is believed to be sufficient to pointout that the scanner motor 70 has an output shaft 72 on which a supportbracket 74 is fixedly mounted. The scanning mirror 66 is fixedly mountedon the bracket 74. The motor 70 is driven to reciprocally andrepetitively oscillate the shaft 72 in alternate circumferentialdirections over arc lengths of any desired size, typically less than360°, and at a rate of speed on the order of a plurality of oscillationsper second. In a preferred embodiment, the scanning mirror 66 and theshaft 72 jointly oscillate so that the scanning mirror 66 repetitivelysweeps the incident laser diode beam impinging thereon through anangular distance or arc length at the reference plane of about 32° andat a rate of about 20 scans or 40 oscillations per second.

Referring again to FIG. 2, the returning portion of the reflected laserlight has a variable light intensity, due to the differentlight-reflective properties of the various parts that comprise thesymbol 100, over the symbol during the scan. The returning portion ofthe reflected laser light is collected by a generally concave, sphericalcollecting mirror 76, and is a broad conical stream of light in aconical collecting volume bounded, as shown in FIG. 2, by upper andlower boundary lines 108, 110, and, as shown in FIG. 3, by opposed sideboundary lines 112, 114. The collecting mirror 76 reflects the collectedconical light into the head along an optical axis 116 (see FIG. 3) alongthe second optical path through a laser-light-transmissive element 78 toa sensor means, e.g. a photosensor 80. The collected conical laser lightdirected to the photosensor 80 is bounded by upper and lower boundarylines 118, 120 (see FIG. 2) and by opposed side boundary lines 122, 124(see FIG. 3). The photosensor 80, preferably a photodiode, detects thevariable intensity of the collected laser light over a field of viewwhich extends along, and preferably beyond, the linear scan, andgenerates an electrical analog signal indicative of the detectedvariable light intensity.

Referring again to FIG. 9, the reference numeral 126 denotes aninstantaneous collection zone subtended by the symbol 100 and from whichthe instantaneous laser spot 106 reflects. Put another way, thephotosensor 80 "sees" the collection zone 126 when the laser spot 106impinges the symbol. The collecting mirror 76 is mounted on the supportbracket 74 and, when the scanner motor 70 is actuated by the trigger 32,the collecting mirror 76 is reciprocally and repetitively oscillatedtransversely, sweeping the field of view of the photodiode lengthwiseacross the symbol in a linear scan. The collection zones 126a, 126bdenote the instantaneous end positions of the linear scan of the fieldof view.

The scanning mirror 66 and the collecting mirror 76 are in a preferredembodiment, of one-piece construction and, as shown in FIG. 8, arelight-reflecting layers or coatings applied to a plano-convex lens 82constituted of a light-transmissive material, preferably glass. The lens82 has a first outer substantially planar surface on a portion of whicha first light-reflecting layer is coated to constitute the planarscanning mirror 66, and a second outer generally spherical surface onwhich a second light-reflecting layer is coated to constitute theconcave collecting mirror 76 as a so-called "second surface sphericalmirror".

The scanning mirror 66 can also be a discrete, small planar mirrorattached by glue, or molded in place, at the correct position and angleon a discrete, front surfaced, silvered concave mirror. As describedbelow, the concave collecting mirror 76 serves not only to collect thereturning portion of the laser light and to focus the same on thephotodiode 80, but also to focus and direct an aiming light beamexteriorly of the head.

Also mounted in the head is a pair or more of printed circuitboards 84,86 on which various electrical subcircuits are mounted. For example,signal processing means having components 81, 82, 83 on board 84 areoperative for processing the analog electrical signal generated by thesensor 80, and for generating a digitized video signal. Data descriptiveof the symbol can be derived from the video signal. Suitable signalprocessing means for this purpose was described in U.S. Pat. No.4,251,798. Components 87, 89 on board 86 constitute drive circuitry forthe scanner motor 70, and suitable motor drive circuitry for thispurpose was described in U.S. Pat. No. 4,387,297. Component 91 on board86 constitutes an aiming light controller subcircuit whose operation isdescribed below. Component 93 on board 48, on which the diode 42 andsensor 80 are mounted, is a voltage converter for converting theincoming voltage to one suitable for energizing the laser diode 42. Theentire contents of U.S. Pat. Nos. 4,251,798 and 4,387,297 areincorporated herein by reference and made part of the instantapplication.

The digitized video signal is conducted to an electrical interlockcomposed of a socket 88 provided on the body portion 14, and a matingplug 90 provided on the handle portion 12. The plug 90 automaticallyelectromechanically mates with the socket 88 when the handle portion ismounted to the body portion. Also mounted within the handle portion area pair of circuitboards 92, 94 (see FIG. 1) on which various componentsare mounted. For example, a decode/control means comprised of components95, 97 and others are operative for decoding the digitized video signalto a digitized decoded signal from which the desired data descriptive ofthe symbol is obtained, in accordance with an algorithm contained in asoftware control program. The decode/control means includes a PROM forholding the control program, a RAM for temporary data storage, and acontrol microprocessor for controlling the PROM and RAM. Thedecode/control means determines when a successful decoding of the symbolhas been obtained, and also terminates the reading of the symbol uponthe determination of the successful decoding thereof. The initiation ofthe reading is caused by depression of the trigger 32. Thedecode/control means also includes control circuitry for controlling theactuation of the actuatable components in the head, as initiated by thetrigger, as well as for communicating with the user that the reading hasbeen automatically terminated as, for example, by sending a controlsignal to an indicator lamp 96 to illuminate the lamp.

The decoded signal is conducted, in one embodiment, along a signalconductor in the cable 46 to a remote, host computer 128 which servesessentially as a large data base, stores the decoded signal and, in somecases, provides information related to the decoded signal. For example,the host computer can provide retail price information corresponding tothe objects identified by their decoded symbols.

In another embodiment, a local data storage means, e.g. component 95, ismounted in the handle portion, and stores multiple decoded signals whichhave been read. The stored decoded signals thereupon can be unloaded toa remote host computer. By providing the local data storage means, theuse of the cable 46 during the reading of the symbols can be eliminated--a feature which is very desirable in making the head as freelymanipulatable as possible.

As noted previously, the handle portion 12 may be one of a set ofhandles which may be interchangeably mounted to the body portion. In oneembodiment, the handle portion may be left vacant, in which case, thevideo signal is conducted along the cable 46 for decoding in a remotedecode/control means. In another embodiment, only the decode/controlmeans may be contained within the handle portion, in which case, thedecoded signal is conducted along the cable 46 for storage in a remotehost computer. In still another embodiment, the decode/control means anda local data storage means may be contained within the handle portion,in which case, the stored decoded signals from a plurality of readingsthereupon may be unloaded in a remote host computer, the cable 46 onlybeing connected to unload the stored signal.

Alternatively, rather than providing a set of removable handles, asingle handle can be non-detachably fixed to the head and, in thisevent, different components mounted on removable circuitboards 92, 94may be provided, as desired, within the single handle by removing, andthereupon replacing, the removable handle end 128.

As for electrically powering the laser diode 42, as well as the variouscomponents in the head requiring electrical power, a voltage signal maybe conveyed along a power conductor in the cable 46, and a converter,such as component 93, may be employed to convert the incoming voltagesignal to whatever voltage values are required. In those embodiments inwhich the cable 46 was eliminated during the reading of the symbols, arechargeable battery pack assembly 44 (see FIG. 7) is detachablysnap-mounted at the bottom of the handle portion 12.

In further accordance with this invention, an aiming light arrangementis mounted within the head for assisting the user in visually locating,and in aiming the head at, each symbol to be read in its turn,particularly in the situation described above wherein the laser beamincident on, and reflected from, the symbol is not readily visible tothe user. The aiming light arrangement comprises means including anactuatable aiming light source 130, e.g. a visible light-emitting diode(LED), an incandescent white light source, a xenon flash tube, etc.,mounted in the head and operatively connected to the trigger 32. Whenactuated either directly by the trigger 32 or indirectly by thedecode/control means, the aiming light 130 propagates and generates adivergent aiming light beam whose light is readily visible to the user,and whose wavelength is about 6600 Angstrom units, so that the aiminglight beam generally is red in color and thus contrasts with the ambientwhite light of the environment in which the symbol is located.

Aiming means also are mounted in the head for directing the aiming lightbeam along an aiming light path from the aiming light source toward thereference plane and to each symbol, visibly illuminating at least a partof the respective symbol. More specifically, as best shown in FIGS. 2and 3, the aiming light 130 is mounted on an inclined support 132 fordirecting the generally conical aiming light beam at the optical element78. The conical aiming light beam is bounded by upper and lower boundarylines 134, 136 (see FIG. 2) and by opposed side boundary lines 138, 140(see FIG. 3) en route to the optical element 78. As previously noted,the optical element 78 permits the collected laser light to pass throughto the photosensor 80, and filters out ambient light noise from theenvironment from reaching the photosensor. The optical element 78 alsoreflects the aiming light beam impinging on it. The optical element is,in effect, a so-called "cold" mirror which reflects light in wavelengthsin the range of the aiming light beam, but transmits light inwavelengths in the range of the laser light. The aiming light beam isreflected from the cold mirror 78 along an optical axis which issubstantially collinear with the optical axis 116 of the collected laserlight between the collecting mirror 76 and the photosensor 80, andimpinges on the concave mirror 76 which serves to focus and forwardlyreflect the aiming light beam along an optical axis which issubstantially collinear with the same optical axis of the collectedlaser light between the concave mirror 76 and the symbol 100. Theconcave mirror 76 which serves as a focusing mirror for the aiming lightbeam focuses the aiming light beam to about a one-half inch circularspot size at a distance about 8 inches to about 10 inches from the nose20 of the head. It will be noted that the portion of the aiming lightpath which lies exteriorly of the head coincides with the portion of thecollected laser light path which lies exteriorly of the head so that thephotosensor 80, in effect, "sees" the non-readily-visible laser lightreflected from that part of the symbol that has been illuminated, orrendered visible, by the aiming light beam. In another variant, theaiming light beam could have been directed to the symbol so as to becoincident with the outgoing incident laser beam by placing a coldmirror in the first optical path and directing the aiming light beam atthe cold mirror so that the optical axis of the aiming light beam iscoincident with that of the outgoing incident laser beam.

As shown in FIG. 10, the aiming LED 130 may, in a first static singlebeam aiming embodiment, be positioned relative to a stationary directingelement 142, e.g. a focusing lens, stationarily mounted in the aiminglight path within the head. The lens 142 is operative for focusing anddirecting the aiming light beam to the respective symbol 100, visiblyilluminating thereon a spot region 150 (see also FIG. 11) within thefield of view. The spot region 150 preferably is circular, near thecenter of the symbol, and is illuminated both prior to the scan tolocate the symbol before the reading thereof, and during the scan duringthe reading thereof. Both close-in and far-out symbols can be locatedand seen by the static single beam aiming embodiment of FIG. 10, thefar-out symbols, due to their greater distance from the head, beingilluminated to a lesser intensity, but visible, nevertheless, by theuser. However, as explained previously, the fixed spot 150 provideslittle assistance in terms of tracking the scan across the symbol.

Turning next to a second static twin beam aiming embodiment, as shown inFIG. 12, a pair of aiming LEDs 130a, 130b, identical to aiming LED 130,are angularly positioned relative to the stationary focusing lens 142which, in turn, is operative to direct the aiming light beams of bothLEDs 130a, 130b to the same respective symbol, visibly illuminatingthereon a pair of spot regions 152, 154 that are within, and spacedlinearly apart of each other along the field of view. The spot regions152, 154 preferably are circular, near the ends of the scan, and areilluminated both prior to and during the scan to locate and track therespective symbol both before and during the reading thereof. Bothclose-in and far-out symbols can be located and seen by the static twinbeam aiming embodiment of FIG. 12, the far-out symbols, due to theirgreater distance from the head, being illuminated to a lesser intensity,but visible, nevertheless, by the user. As explained previously, thepair of fixed spots 152, 154 provide valuable assistance in terms oftracking the scan across the symbol.

Turning next to a third dynamic single beam aiming embodiment and withthe aid of FIG. 11, rather than stationarily mounting the focusing lens142 in the head, the lens 142 may be oscillated in the manner describedpreviously for the scanning/collecting/focusing component to sweep theaiming light beam across the respective symbol, illuminating thereon aline region 156 (see FIG. 13) extending along the field of view. Theline region 156 is illuminated during the scan to track the respectivesymbol during the reading thereof. Close-in symbols are well illuminatedby the line region 156, even when the scan is performed at rates of 40scans per second; however, for far-out symbols, the greater the distancefrom the head and the faster the scan rate, the less visible is the lineregion 156.

Returning to FIGS. 1-6, a combination static/dynamic aiming arrangementis shown which is actuated by the trigger 32 among various positions orstates. In FIG. 2, the trigger 32 is shown in an off state, wherein allthe actuatable components in the head are deactivated. A pair ofelectrical switches 158, 160 are mounted on the underside of board 84.Each switch 158, 160 has a spring-biased armature or button 162, 164which, in the off state, extend out of the switches and bear againstopposite end regions of a lever 166 which is pivoted at a center-offsetposition at pivot point 168 on a rear extension 170 of the trigger 32.

When the trigger 32 is initially depressed to a first initial extent, asshown in FIG. 5, the lever 166 depresses only the button 162, and thedepressed switch 158 establishes a first operational state in which thetrigger 32 actuates the aiming light 130 whose aiming light beam isthereupon reflected rearwardly off cold mirror 78 and reflectedforwardly off the focusing mirror 76 to the symbol. In the firstoperational state, the trigger has also positioned the focusing mirror76 in a predetermined stationary position. The stationary focusingmirror 76 directs the aiming light beam to the symbol, visiblyilluminating thereon a spot region, identical to central spot region 150in FIG. 11, within the field of view prior to the scan to assist theuser in locating the symbol before the reading thereof. The stationarypositioning of the focusing mirror 76 is advantageously accomplished byenergizing a DC winding of the scanner motor 70 so that the output shaftand the focusing mirror 76 mounted thereon are angularly turned to acentral reference position.

Thereupon, when the trigger 32 is depressed to a second further extent,as shown in FIG. 6, the lever 166 depresses not only the button 162, butalso the button 164, so that a second operational state is established.In the second operational state, the trigger actuates all the remainingactuatable components in the head, e.g. the laser diode 42, the controlcircuitry of the scanner motor 70 which causes the focusing mirror 76 tooscillate, the photodiode 80, the signal processing circuitry, as wellas the other circuitry in the head, to initiate a reading of the symbol.The focusing mirror 76 no longer is stationary, but is being oscillatedso that the aiming light beam dynamically is swept across the symbol,visibly illuminating thereon a line region, identical to line region 156in FIG. 13, extending along the field of view. Hence, during the scan,the user is assisted in tracking the symbol during the reading thereof.Such symbol tracking is highly visible for close-in symbols, but less sofor far-out symbols.

The aforementioned sequential actuation of the components in the headcould also be done with a single two-pole switch having built-insequential contacts.

Returning to FIGS. 2 and 3, it will be noted that many of the variouscomponents in the head are shock-mounted by a front shock isolator 172on which the board 48 and all the components thereon are supported, andby a rear shock isolator 174 on which a support plate 176 on which thescanner motor 70 and the aiming light 130 are supported. A light baffle178 subdivides the interior of the body portion and assists the coldmirror 78 in preventing stray ambient light from reaching thephotosensor 80.

The laser scanning head of FIG. 2 is of the retro-reflective typewherein the outgoing incident laser beam, as well as the field of viewof the sensor means, are scanned. It will be readily understood thatother variants also are within the spirit of this invention. Forexample, the outgoing incident laser beam can be directed to, and sweptacross, the symbol through one window on the head, while the field ofview is not scanned and the returning laser light is collected throughanother window on the head. Also, the outgoing incident beam can bedirected to, but not swept across, the symbol, while the field of viewis scanned.

A variety of housing styles and shapes dictated by such considerationsas esthetics, environment, size, choice and placement of electronic andmechanical components, required shock resistance both inside and outsidethe housing, may be employed in place of the housing shown in thedrawings.

The laser scanning head of this invention need not be hand-held, but canalso be incorporated in a desk-top, stand-alone workstation in which thesymbol is passed through the workstation, preferably underneath anoverhead window or port through which the outgoing incident laser beamis directed. Although the workstation itself is stationary, at leastduring the scanning of the symbol, the symbol is movable relative to theworkstation and must be registered with the outgoing beam and, for thispurpose, the aiming light arrangement described herein is particularlyadvantageous.

It should be noted that the laser scanning head of this invention canread high-, medium- and low-density bar code symbols within approximateworking distance ranges of 1" to 6", 1" to 12", and 1" to 20",respectively. As defined herein, the high-, medium- and low-density barcode symbols have bars and/or spaces whose smallest width is on theorder of 7.5 mils, 15-20 mils and 30-40 mils, respectively. In thepreferred embodiment, the position of the reference plane for a symbolof a known density is optimized for the maximum working distance forthat symbol.

To assist the user in aiming the head at the symbol, in addition to theaiming light arrangements described herein, other means may be provided.For example, a mechanical aiming means such as a raised sighting elementformed on an upper portion of the housing and extending along thedirection of the first or second optical path may be sighted along bythe user. A viewport having a sight window may also be located on thehead to enable the user to look through the sight window and therebyvisually locate the symbol in the window. A sonic ranging means can alsobe used for finding the symbol. The ranging means emits a sonic signal,detects a returning echo signal, and actuates an auditory indicator uponsuch detection. The auditory indicator can sound a tone or change therate of a series of sounds or beeps, thereby signaling the user that thesymbol has been found.

In another aspect of this invention, it is sometimes desirable to causethe aforementioned aiming light spots on the symbol to blink, e.g. forthe purpose of making the spots easier to see, or to reduce the averagepower consumed by the aiming light sources. Such blinking light spotscan be effected by electrical and/or mechanical means.

FIG. 14 is analogous to FIG. 2, and illustrates a currently preferredcommercial embodiment of the laser scanning head. For the sake ofbrevity, like parts in FIG. 14 have been identified by primed numeralsas compared to corresponding parts in FIG. 2.

As for the differences between the FIG. 2 and FIG. 14 embodiments, oneimportant distinction shown for the head 10' in FIG. 14 is that the bodyportion 14' is composed of two housing portions, namely, upper housing180 and lower housing 182, which are assembled together, preferably by asnap-fit engagement. The lower housing 182 is constituted of alight-blocking opaque material such as colored synthetic plasticmaterial, but the upper housing 180 is constituted of alight-transmissive transparent synthetic plastic material. Since boththe outgoing light and the incoming light can pass through thetransparent upper housing 180, a cover 184 of light-blocking materialcovers the entire exterior surface of the transparent upper housing 180,except for a window region 186 and an indicator region 188. The cover184 is constituted of an injection-molded thermoset rubber-like materialwhose interior surface closely matches and conforms to the outer surfaceof the upper housing 180 so as to be in intimate contact with the entireexterior surface thereof and to be frictionally held thereon. The snuglyfitting cover, in effect, masks all the portions of the transparentupper housing 180, other than the window region 186 and the indicatorregion 188, and prevents any outgoing light or incoming light frompassing therethrough.

Thus, it is no longer necessary, as in prior art heads, to separatelyglue or mount a discrete window in place on the head. The uncoveredwindow region 186 serves as the window for both outgoing and incominglight. The uncovered window region 186 is, of course, of a one-piececonstruction with the remainder of the upper housing 180 and, hence, nolonger does the possibility exist, as in the prior art, that a windowcould become free of its mounting and permit dust, moisture and othersuch contaminants from coating or interfering with the proper operationof the optics and the electrical components within the head.

In addition, the indicator region 188 is not covered by the cover 184,so that light from the indicator lamp 96' can shine therethrough. Again,the prior art necessity to mount a separate window at the region of theindicator lamp 96' has been eliminated, thereby further contributing tothe very effective sealing of the interior of the head.

The rubber-like cover is preferably thick, cushionable, and yieldable,and provides a measure of shock-resistance for the head. It further willbe noted from FIG. 14 that the cover has bent-under flanges at theregion of the juncture between the upper and lower housings 180, 182 toprovide a very effective gasket-like seal.

Still another difference between the FIG. 2 and FIG. 14 embodiments isthe provision of a sealing diaphragm 190 in the region of the trigger32'. The sealing diaphragm 190 has a central actuator 192, one surfaceof which engages button 164' of switch 160'. The opposite surface of theactuator 192 engages a ramp portion 194 of the trigger 32'. Inoperation, whenever the trigger is manually depressed, the ramp portion194 urges the actuator 192 into engagement with the button 164' toactuate the switch 160'. During this operation, the diaphragm 190isolates the interior of the head from the exterior thereof in theregion of the trigger, thereby closing off another avenue through whichdust, contaminants, moisture, etc. could otherwise freely enter as inthe prior art.

Still another distinction between the FIG. 2 and FIG. 14 embodiments isthat the laser diode, the optical assembly, the aiming light and themotor portion of the scanner motor are all mounted within and on acommon support also known as an optical cradle 200. The cradle 200 hasan upper part 202 and a lower part 204 which are assembled together asfollows. At the front end of the cradle, a projection 206 on the upperpart 202 is passed through and snappingly engages behind a recess 208formed in a channel provided on the lower part 204. At the rear of thecradle, a threaded fastener 210 passes through a clearance hole in lowerpart 204 and threadedly engages a threaded hole formed in the upper part202. The front shock isolator 172' is located between the front of thehousing and the front of the cradle 200, and the rear shock isolator174' is located between the rear of the cradle and inwardly-extendingpartitions 175,177 provided at the rear of the head.

Still another difference lies in mounting the printed circuitboard 86'not above the printed circuitboard 84', but instead, in arearwardly-extending compartment 212 formed between the aforementionedpartitions 175, 177 and the rear wall of the body portion 14'.

Another difference lies in the provision of an O-ring seal 214 mountedin an annular groove formed at the inner end region of the handle insert128'. It will be understood that each of the elements described above,or two or more together, also may find a useful application in othertypes of constructions differing from the types described above.

FIG. 15 illustrates yet another preferred embodiment of an opticalsystem. The optical system of FIG. 15 may be incorporated into thescanner head styles of FIGS. 2 and 14, or in the scanner head styleillustrated in FIG. 16.

The optical system of FIG. 15 includes a source of laser light 216. Thesource of laser light 216 may include a helium-neon laser tube or alaser diode, whether visible or non-readily visible as previouslydefined. The source of laser light 216 also may include the collimatingoptics for beam forming and shaping as previously described.

The optical system of FIG. 15 further includes a folding mirror 218. Asshown in FIG. 15, the folding mirror 218 may be affixed to a curvedcollecting mirror 220. Alternatively, the folding mirror 218 may bemounted to a support within the scanning head, so long as it is mountedin a fixed, stationary relationship to the collecting mirror 220. Eitherway, the folding mirror is mounted at the proper angle to direct theincident laser light onto a scanning mirror 232 as described below.

The collecting mirror 220 is mounted to a support bracket 222. The laserlight source 216 emits a beam of coherent, collimated laser light to thefolding mirror 218 along a first optical path 224. As previouslydefined, the incident laser light travels along a first optical pathfrom the laser light source 216 to an indicia 226. This first opticalpath is shown in FIG. 15 as a solid line with arrow heads. The incidentlaser light is reflected by the indicia 226 where it returns to adetector 228, such as a photodetector, along a second optical path 230,shown in FIG. 15 as a set of dashed lines.

The light-weight, movable scanning mirror 232 receives the incidentlaser light in the first optical path and reflects this laser light tothe indicia 226. The scanning mirror 232 also receives reflected laserlight in the second optical path from the indicia 226 and reflects thislight to the collecting mirror 220. The collecting mirror 220 ispreferably spherically concave. The collecting mirror 220 receives thereflected laser light from the scanning mirror 232 and focusses thislight onto the detector 228.

The scanning mirror 232 is mounted on a shaft 234 of a scanning motor(not shown). The scanning mirror 232 preferably reciprocally oscillatesa plurality of times per second, typically 40 scans per second, as shownby arrows 236, about an axis 238. This reciprocal oscillation of thescanning mirror provides a bi-directional scan of the laser light on theindicia 226. The shaft 234 may simply rotate the scanning mirror 232,providing a uni-directional scan of the laser light on the indicia 226.

FIG. 16 depicts the various components just described as they aremounted in one style of a scanning head. The source of laser light 216generates a coherent, collimated light beam along a first optical path224. This light beam strikes a folding mirror 218 which reflects thelight beam to a scanning mirror 232. The scanning mirror 232 develops ascanning light beam, directing the scanning light beam to the indicia226 (FIG. 15). The indicia 226 reflects this light, now of varyingintensity, back to the scanning mirror 232. The scanning mirror reflectsthe light onto the collecting mirror 220, which focusses the light ontothe detector 228. The detector 228 senses the varying intensity of thelight to develop an analog electrical signal and the scanning headprocesses this signal in the conventional manner.

As shown in FIG. 16, the scanning head may operate completelyindependently of a power cord or a signal cord. In this way, a batterypack (not shown) provides electrical power to all of the variouscomponents in the scanning head. The scanning head also develops a radiofrequency (RF) signal for transmission to a host processor for furtherprocessing. The scanning head may also include a receiver to receivetransmissions from the host processor to control various features of thescanning head.

While the invention has been illustrated and described as embodied in aportable laser diode scanning head, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

We claim:
 1. A laser scanning head for reading symbols comprising:(a) anactuatable laser light source mounted in the head and operative, whenactuated, for generating an incident laser beam; (b) a stationaryfolding mirror for reflecting the incident laser beam along a firstoptical path; (c) a movable scanning mirror positioned in the firstoptical path so as to reflect the incident laser beam directly to areference plane located exteriorly of the head, and to a symbol locatedin a working distance range in the vicinity of the reference plane,thereby reflecting off the symbol reflected laser light, at least areturning portion of which travels along a second optical path away fromthe symbol directly back to the scanning mirror; (d) a stationary,curved collecting mirror having the folding mirror mounted in a centralarea thereof, the collecting mirror being larger than the foldingmirror; (e) a scan drive means mounted in the head for moving thescanning mirror and for sweeping the incident laser beam in a scanacross the symbol, the returning portion of the reflected laser lighthaving a variable intensity over the scan; (f) a sensor mounted in thehead for detecting the variable intensity of the returning portion ofthe reflected laser light over a field of view, and for generating anelectrical analog signal indicative of the detected variable lightintensity, the curved collecting mirror positioned to collect thereturning portion of the reflected laser light over the field of viewand to direct the collected returning portion to the sensor; (g) asignal processor mounted in the head for processing the analogelectrical signal, and for generating a processed signal indicative ofthe symbol; and (h) a manually-actuatable trigger on the head andoperatively connected to and operative for actuating, the scanningmirror, the laser light source, the scan drive means, the sensor, andthe signal processor, to initiate a reading of the symbol upon manualactuation of the trigger by the user.
 2. The head as recited in claim 1,wherein the incident laser beam is non-readily visible to a user.
 3. Anoptical component for use in optical scanning systems of the type havinga light source and a light sensor, and operative for reading indiciahaving parts of different light reflectivity, comprising:(a) astationary folding mirror for reflecting light from the light source;(b) a scanning mirror(i) for reflecting light from the folding mirrordirectly to the indicia parts in a scan across the indicia parts,thereby reflecting light of variable light intensity off the indiciaparts, (ii) for directly receiving at least a portion of the lightreflected off the indicia parts; (c) a stationary curved collectingmirror positioned in a fixed relationship with the folding mirror, thefolding mirror being located near a central area of the collectingmirror and the collecting mirror being larger than the folding mirror,the scanning mirror further serving to direct the received portion ofthe light reflected off the indicia parts onto the collecting mirror,the collecting mirror positioned to focus the light from the scanningmirror onto the detector; and (d) means for moving the scanning mirror.4. The component as recited in claim 3, wherein the curved collectingmirror has an optical axis.
 5. The component as recited in claim 3,wherein the light source is a laser source, and wherein the indiciaconstitute bar code symbols.
 6. The component as recited in claim 5,wherein the laser light source produces a non-readily visible light. 7.An optical component for use in optical scanning system of the typehaving a laser light source and a laser light sensor mounted in alightweight handheld housing, and operative for reading indicia havingparts of different light reflectivity, comprising:(a) a stationaryfolding mirror mounted in the path of the light from the light source;(b) a reciprocally oscillatable scanning mirror for reflecting lightfrom the folding mirror directly to the indicia parts in a scan acrossthe indicia parts, thereby returning light of variable light intensityreflected off the indicia parts at least a portion of which is directlyreceived and reflected by the scanning mirror; (c) a stationarycollecting mirror for collecting a least a portion of the returninglight reflected by the scanning mirror, and for directing the collectedportion of light to the light sensor; wherein the folding mirror issmaller than, and is positioned near a central area of the collectingmirror; and (d) drive means for oscillating the scanning mirror.
 8. Thecomponent as recited in claim 7, wherein the folding mirror is one-piececonstruction with the collecting mirror.
 9. The component as recited inclaim 7, wherein the folding mirror has a front surface facing the lightsource and covered with a light-reflecting coating, and wherein thecollecting mirror has a front surface facing the light sensor andcovered with a light-reflecting coating.
 10. The component as recited inclaim 7, wherein the oscillating means includes a scanner motor havingan output shaft on which the scanning mirror is mounted, the motor beingoperative for reciprocally and repetitively oscillating the shaft inalternate circumferential directions over arc lengths less than 360° andat a rate of speed on the order of a plurality of oscillations persecond.
 11. The component as recited in claim 7, wherein the lightsource is a laser source, and wherein the indicia constitute bar codesymbols.
 12. The head as described in claim 7, wherein the scanningmeans includes an electric motor having an output shaft, and thescanning mirror is mounted for direct movement with the output shaft.13. A lightweight, handheld laser scanner for reading indicia andgenerating electrical signals indicative thereof, comprising:(a) ahousing having an area for passing laser light to the indicia and forreceiving reflected laser light from the indicia; (b) a source of laserlight in the housing; (c) a sensor in the housing for receiving thereflected laser light after it has been admitted through the area andfor generating a first signal representative of the indicia; (d) aplurality of optical elements positioned in the housing generallydefining an optical path between the source of laser light and the areaof the housing and between the area and the sensor, the optical elementsincluding (i) a stationary folding mirror for receiving laser emissionsfrom the light source, (ii) a reciprocally oscillatable scanning mirrorpositioned for receiving laser emissions from the folding mirror andsweeping them directly through the area and across the indicia, and forreceiving light reflected directly from the indicia through said area,and (iii) a stationary collecting mirror positioned for receiving thereflected laser light from said scanning mirror and reflecting it ontothe sensor, wherein the folding mirror and the collecting mirror aresecured in a fixed physical relationship with respect to each other, thefolding mirror being smaller than the collecting mirror and positionedadjacent a central area thereof; and (e) drive means for reciprocallyoscillating the scanning mirror.
 14. The scanner according to claim 13and including signal processing circuitry in the head for processing thefirst signal into a digital signal.
 15. The scanner according to claim13 and including a trigger supported by the housing and operativelyconnected to the laser light source and to the drive means forinitiating the scanning of the indicia.
 16. The scanner as described inclaim 13 wherein the drive means includes an electric motor having anoutput shaft, and the scanning mirror is mounted for direct movementwith the output shaft.
 17. A method for bar code scanning, comprisingthe steps of:generating a light beam utilizing a light source;reflecting the generated light beam to an oscillating scanning mirrorutilizing a stationary folding mirror; reflecting the light beam fromsaid scanning mirror utilizing the scanning mirror directly to a fieldlocated outside the scanning apparatus; at least a portion of the lightreceived by the field being returned directly back to the scanningmirror; reflecting said returned light by the scanning mirror to aconcave stationary collecting mirror, wherein the collecting mirror islarger than the folding mirror and the folding mirror is mounted near aline intercepting a central area of the collecting mirror; andreflecting said returned light by the collecting mirror to a lightsensor.
 18. A light scanning assembly for distinguishing lightreflective indicia comprising:(a) a forward portion of the assemblyspaced from said indicia, and a rearward portion disposed further fromsaid indicia than said forward portion; (b) an actuatable laser lightsource mounted on said assembly and operative, when actuated, forgenerating an incident laser beam; (c) a stationary folding mirror onsaid assembly for reflecting said incident laser beam along a firstoptical path; (d) a movable scanning mirror on said rearward portion ofsaid assembly, positioned in said first operable path so as to reflectsaid incident laser beam directly to a reference plane located exteriorto said assembly, into a symbol located in a working distance range inthe vicinity of the reference plane, thereby reflecting off said symbolreflected laser light, at least a returning portion of which travelsalong a second optical path away from said symbol directly back to saidscanning mirror; (e) a stationary, curved collecting mirror having saidfolding mirror disposed in the light path of a central area thereof,said collecting mirror being larger than said folding mirror; (f) a scandrive mounted on said assembly for moving said scanning mirror to causea sweeping of said incident laser beam in a scan across the symbol, thereturning portion of the reflected laser light having a variableintensity over said scan; and (g) a sensor mounted in said assembly fordetecting the variable intensity of the returning portion of thereflected laser light over a field of view, and for generating anelectrical analog signal indicative of the detected variable lightintensity, said curved collecting mirror positioned to collect thereturning portion of the reflected laser light over the field of viewand to direct the collected returning portion to said sensor.